It is sometimes desirable to supply electrical power to consumers situated far away from electrical power infrastructures. There are several solutions to this problem. One way to get electrical power is to have locally placed engine generators. Sometimes three phase high voltage distribution lines are used. A system called SWER, Single Wire Earth Return, use a one phase single wire cable. It can transmit single phase high voltage current from 6 kV to 19.1 kV. It is made for power up to 500 kW.
Problems that occur in these solutions normally relates to resistive voltage drop, sensibility to disturbances and detection of faults, e.g. earth fault detection, phase fault and loosing of phases. Some systems are complicated and costs and maintenance can sometimes be an important issue. The solutions can also have problems to comply with local authorities safety regulations.
One example of small power consumers that could be situated in places far away from electrical infrastructure is telecom equipment, such as radio base stations. Two diesel generators with back up batteries are often used for locally produced power. This requires a costly maintenance organisation and the sites operational reliability is dependent on a well-functional logistic organisation and accessibility to these sites. Sometimes a high-voltage distribution system has been used, e.g. 12 kV or 24 kV three phase distribution line. For shorter distances 1 kV is sometimes used.
The purpose of the inventions is to overcome the disadvantages described above.